Electrical interconnectors

ABSTRACT

A 15 kv cable joint is enclosed within two half shells filled with sealant material. Displacement or thermal expansion of the sealant is accommodated by various configurations of stress cones that have apertures or surfaces that are flexible and arranged to maintain pressure on the sealant for example during thermal cycling of the joint.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the protection of electrical interconnections.Such interconnections may be between two or more electrical cables (i.e.in-line or branch joints), between two or more pieces of otherelectrical equipment such as transformers and switchgear, but which mayalso include another cable or between cable and equipment, includingcable adapters and terminations. Such an interconnection usually needsto be protected against ingress of moisture to interconnectedconductors, and to provide electrical insulation therearound.Additionally, at voltages above about 10 kV, some form of electricalstress control is usually also desired. The invention is generallyapplicable to electrical interconnections at low voltage, typicallyaround 1 to 10 kV, at medium voltage, typically around 10 to 36 kV, andalso at high voltage, typically greater than 36 kV.

2. Description of the Related Art

Various technologies exist for protecting such interconnections, some ofwhich are more applicable to one voltage range rather than another, andsome applicable to cables, for example, of one material, for examplepolymeric, then another, for example paper. Amongst these technologiesmay be mentioned polymeric heat shrink, elastomeric push -on androll-on, elastomeric hold-out, tape winding, hot bitumen filling, andcold-pour resin systems. Pending Raychem U.S. patent application Ser.No. 08/138360 the contents of which are now published in InternationalApplication Publication No. WO 95/11543, discloses a power cable jointwhich is filled by a compressible sealant material such as gel, whichhas been found to have surprisingly good performance.

SUMMARY OF THE INVENTION

The present invention is particularly concerned with an interconnectionbetween two conductive components in which a compressible, andpreferably oil-extended polymeric, sealant material is employed to sealand to provide electrical insulation around the connection, and in whicha conductive member is disposed around the connection in the manner of aFaraday Cage.

Thus, in accordance with one aspect of the present invention, there isprovided an enclosure arranged to enclose a connection between twoelectrically conductive components, the enclosure comprising a rigidhousing and an electrically conductive member disposed therein, theconductive member being arranged, in operation, to make electricalcontact with and sealingly enclose the connection, wherein the spacebetween the conductive member and the housing is, in operation,substantially filled with a compressible sealant material, and whereinthe conductive member is resilient, substantially to prevent, inoperation, the formation of voids within the housing outside theconductive member.

The resilient conductive member may be arranged to exert a pressure onthe sealant material so as substantially to prevent the formation ofvoids therein or between that material and other parts of theinterconnection.

At least one void or gaseous entrapment may be provided completelywithin the conductive member and/or between the conductive member andthe connection of the two conductive components.

The enclosure may enclose an interconnection between an electric powercable, whose conductor provides one of the conductive components of theinvention, and another piece of electrical equipment which may itself beanother power cable. The conductive member may then act as a FaradayCage and may, for example, enclose a jointed pair of conductors in acable splice.

The enclosure of the present invention may also comprise a stress-reliefcone, arranged to be disposed around an electric power cable that formsone of the conductive components for example. Advantageously, the stresscone comprises resilient aperture means that is arranged to change itsvolume in response to a change in volume of the sealant material.

The enclosure may also comprise a housing of which at least a portion ofa wall thereof is resilient so as to respond to change in volume of thesealant material.

The interconnection may comprise location means arranged to support theconductive member and to maintain its position within the sealantmaterial.

The enclosure may comprise a sealing member, acting as a stress-reliefcone for example, and the sealing member advantageously comprises (a) arelatively rigid component and (b) a relatively resilient component,which may have at least one aperture therein. The relatively rigidcomponent is arranged to urge the relatively resilient component intosubstantially complete conformity around the substrate, and the sealingmember is thus able to accommodate a range of substrates, electric powercables for example, of different sizes, usually diameters, whilstmaintaining a good, substantially void-free seal therearound.

The housing used in the invention, preferably formed from twointer-engaging half shells, is preferably made of a conductive polymericmaterial, having a volume resistivity of the order 10³ ohm-cm.Advantageously its material is carbon-filled polypropylene.Alternatively, the housing may have an insulating inner component and aconductive outer component, to provide the required screening function.As other options for the housing, may be mentioned a push-on arrangementthat is stretched over the interconnection, or a revolving sleeve asdisclosed in U.S. Pat. No. 4,868,967. The housing that seals theelectrical interconnection advantageously has at least a portion of awall thereof that is subject to the pressure of the sealant materialformed so as to flex in order to accommodate change of volume of thesealant material. The resilient wall section may be bounded externallyby a non-resilient wall portion so as to define a displacement cavitytherebetween, which cavity may contain resilient means. It is alsoenvisaged that a major part of the housing surface (ie >50%), andadvantageously substantially the whole of that part of the surface thatperipherally encloses the sealant material, is resilient. The housingmay be deformable such that it is able to change from a cross-section ofone shape to a cross-section of a different shape that encloses a largervolume. For example, the housing may be arranged to change from agenerally oval to a substantially circular cross-section.

In order to contain the sealant material, particularly though notexclusively when it is a material such as an oil-extended polymer, whenit is subject to a compressive force on closing therearound of ahousing, formed from two half-shells for example, it is preferred thatthe closing edges of the housing overlap before final closure takesplace, and thus before significant displacement pressure is exerted onthe sealant material. In the case of two longitudinally-extendinghalf-shells, for example, a projection along the longitudinal edge ofone half may engage a channel along the other edge. The sealant materialis thus circumferentially contained within the closing housing beforesufficient pressure is exerted on the sealant material to exude itlaterally out of the housing.

Means may be provided to restrain movement of the housing rotationallyand/or longitudinally with respect to its substrate, which may be anelectrical interconnection for example.

A flexible part of the closed housing, or of another component withinthe joint that is subject to, and contains the pressure of, the sealantmaterial, may be arranged such that the flexible portion follows anycontraction of the sealant material so as to avoid the formation of anypockets of air.

The Faraday Cage member is preferably of a conductive thermoplasticmaterial of similar resistivity to that of the conductive housing, butit may alternatively be formed of metal or metallised plastics material.The conductive Faraday Cage member is advantageously resilient so as toexert pressure on the sealant material, thereby substantially to preventthe formation of voids within the housing outside the conductive membercontained therein. Preferably, the conductive member has at least onevoid or gaseous entrapment completely contained therewithin that issubject to the pressure of the sealant material. The support cradle forthe Faraday Cage is preferably formed of an insulating thermoplasticsmaterial. The support member can conveniently be secured to the housingso as positively to locate the conductive Faraday Cage member within theflowable sealant material.

The stress cone used in the invention may be made of a conductive rubberor elastomeric material, EPDM for example, typically of volumeresistivity 10³ ohm-cm.

The enclosure may comprise an electrical stress cone that comprisesresilient aperture means that is arranged to change its volume inresponse to a change of volume or a displacement of the sealant materialthereby, in operation, to maintain substantially complete filling of thehousing around an electrical interconnection without the formation ofvoids therein.

It is to be understood that the materials of each of the components usedin the invention are to be selected so as to be compatible with anycomponent with which they come into contact and so as not to have anyadverse reaction therewith, especially over longer time periods.

The sealing is typically required to provide a block to the passage ofair, moisture, or other fluids.

The sealing material of the invention may generally comprise anycompressible sealing material, e.g. mastic or grease (especially ahighly viscous grease such as a silicone grease). Preferably, however,the sealing material comprises cured gel.

The gel may, for example, comprise silicone gel, urea gel, SEBS, SBS,di- and tri-block copolymers and blends thereof, urethane gel, or anysuitable gel or gelloid sealing material. Preferred gels compriseoil--extended polymer compositions. Preferably the gel has a hardness atroom temperature as determined using a Stevens-Voland Texture Analyserof greater than 48 g, particularly greater than 14 g especially greaterthan 18 g, e.g. between 18 g and 29 g. The test settings of the Analysershould be: speed =0.2 mm/sec; penetration =4 mm; and sphere diameter=0.25 inch. It preferably has a stress-relaxation less than 60%,particularly less than 50% and especially less than 40% and preferablygreater than 10%. Ultimate elongation, also at room temperature, ispreferably greater than 100%, especially greater than 200%, particularlygreater than 400%, as determined according to ASTM D638. Tensile modulusat 100% strain is preferably at least 1.8 MPa more preferably at least2.2 Mpa. In general compression set will be less than 25%, especiallyless than 15%. Preferably, the gel has a cone penetration as measured byASTM D217 of at least 50 (10⁻¹ mm), more preferably at least 100 (10⁻¹mm), even more preferably at least 200 (10⁻¹ mm) and preferably nogreater than 400 (10⁻¹ mm), especially no greater than 350 (10⁻¹ mm).Reference is also made to U.S. Pat. No. 4,852.646, especially FIG. 3thereof, for alternative gel parameters., showing the relationshipbetween the Voland Hardness and the Cone Penetration value, the entirecontents of which are included herein by this reference. Also, referenceis made to the suitable materials disclosed in U.S. Pat. No. 5,079,300,the entire contents of which are included herein by this reference.

Alternatively, the polymer composition of the gel may for examplecomprise an elastomer, or a block copolymer having relatively hardblocks and relatively soft elastomeric blocks. Examples of suchcopolymers include styrene-diene block copolymers, for examplestyrene-butadiene or styrene-isoprene diblock or triblock copolymers, orstyrene-ethylene-butylene-styrene triblock copolymers as disclosed ininternational patent publication number W088/00603. Preferably, however,the polymer composition comprises one or morestyrene-ethylene-propylene-styrene block copolymers, for example as soldunder the Trade Mark `Septon` by Kuraray of Japan. Septon 2006 is aparticularly preferred grade. The extender liquids employed in the gelpreferably comprise oils conventionally used to extend elastomericmaterials. The oils may be hydrocarbon oils, for example paraffinic ornaphthenic oils, synthetic oils for example polybutene or polypropeneoils, and mixtures thereof. The preferred oils are mixtures ofnon-aromatic paraffins and naphthenic hydrocarbon oils. The gel maycontain known additives such as moisture scavengers (eg. Benzoylchloride), antioxidants, pigments and fungicides.

The gel used in the present invention advantageously has a dielectricbreakdown strength of at least 18 KV/mm, preferably greater than 24KV/mm, being in the preferred range of 24 to 50 KV/mm, but could even beas high as 100 KV/mm. These values apply not only to the bulk values ofthe gel itself, but also to any interface between the gel and othermaterials with which it has contact in the interconnection. Thepreferred gel material comprises a silicone gel, being a siliconepolymer extended with an inert silicone oil.

It will be understood from this document that the term "compressible" inthe context of the sealant material refers to a material that, uponbeing subject to an external pressure, is compressible so as to flowaround an enclosed substrate. The pressure may arise from the housingthat contains the sealant material being applied to, for example closedaround, the electrical interconnection, or from thermal expansion of thesealant material. With the preferred sealant material being a gel, thecompressive force results in deformation and/or displacement that allowssubstantially complete conformity with the substrate, which conformitycan be maintained even under thermal cycling.

The connection will typically be of substantially cylindricalconfiguration. The present invention is of particular applicability inconnections in which the housing consists of two, or more,inter-engaging components, for example two half-shells. In such aconfiguration, the stress cone is also advantageously formed of aplurality of components, for example two half-cones that mate on closureof the housing, so that the interconnection can conveniently be formedin a wraparound manner around the already-made electrical connection,for example a crimp. Conveniently, the gel sealant is supplied as afilling contained within each part of the housing, which then seals theinterface therebetween. The advantages of this configuration, especiallywhen using a gel as the sealant, are discussed in pending Raychem U.S.patent application Ser. No. 08/138360 (WO 95/11543), the entire contentsof which are included herein by this reference. In particular, thesurprisingly high dielectric strength found at the interface of the twoportions of the gel, and the excellent adhesion of the gel to thecomponents of the interconnection, such as the cable materials (usuallypolyethylene or polyvinylidene chloride), substantially prevent airpockets to exist therebetween and allow a cable joint, for example, tobe made of a much-reduced length than has previously been possible. Ashorter length joint requires less cable preparation, and thus less timeto complete, this being particularly so when the cable system is buriedin the ground.

In accordance with another aspect of the present invention, there isprovided an interconnection between a electric cable and another pieceof electrical equipment, the interconnection being enclosed within anenclosure in accordance with the first aspect of the invention.

The other piece of electrical equipment may be, for example, anotherelectrical cable, or equipment such as switchgear or a transformer towhich the said cable is connected, or other equipment at which the saidcable is terminated. Enclosures and interconnections in accordance withthe present invention are hereinafter described especially withreference to FIGS. 1 and 13 of the accompanying drawings, but it isenvisaged that features of other Figures may also be included in suchenclosures for interconnections, for example the features associatedwith the stress cone (FIGS. 1 to 6 and 8), the Faraday Cage (FIGS. 1 and13) and its support member (FIGS. 1, 21 and 22,) and the housing (FIGS.1, 6, 14, to 20 and 23 to 25). Some of these features are the subject ofour patent applications filed contemporaneously herewith, under ourreferences RK502, RK505 and RK506, the entire disclosures of which areincorporated herein by this reference.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 shows schematically a cross-sectional elevation of an in-linejoint between two screened 15kV power cable joints, for demonstratingthe general principles of the invention;

FIGS. 2. 2A show schematically a first embodiment of the invention inwhich a stress-relief cone of the joint of FIG. 1 is arranged toaccommodate expansion of sealant material of the joint;

FIG. 3 shows another form of stress cone to that of FIG. 2;

FIGS. 4. 4A show still another form of stress cone, in section and inisometric view respectively;

FIGS. 5. 5A show another variation of the cable joint of FIG. 1, inwhich sealant expansion is accommodated, in section and in isometricview respectively;

FIG. 6 shows a partial section through one half of a modified joint:

FIG. 7 shows another form of stress cone for use with the joint of FIG.1;

FIG. 7A shows a cutaway view of the stress cone of FIG. 7;

FIG. 7B shows a reverse angle isometric view of the stress cone of FIG.7;

FIG. 8 shows a further modification of a stress cone for accommodatingsealant expansion within the joint of FIG. 1;

FIG. 9 shows a dis-assembled view of one half of a modified arrangementof outer housing and stress-relief cones for use in the general jointconstruction of FIG. 1;

FIG. 10 shows a cross-section through a completed joint employing astress cone as shown in FIG. 9;

FIGS. 11 and 12 are isometric views of the rear end of one half of amodified range-taking stress cone;

FIGS. 13A, 13B and 13C illustrate schematically features applicable tothe Faraday Cage of the joint of FIG. 1 for accommodating expansion ofthe sealant material of the joint;

FIG. 14 shows schematically one modification of the housing of the jointof FIG. 1 for accommodating expansion of the sealant material;

FIG. 15 shows a further modification of the housing of FIG. 1;

FIG. 16 shows an isometric view of one half of a further modification,in which an integral insert provides for gel expansion and includesstress cones;

FIGS. 17 and 18 show sections along lines B--B and A--A respective ofFIG. 16;

FIGS. 19 and 20 schematically show a modification of the outer housingof the joint, formed from three components;

FIG. 21 shows schematically one arrangement in which a Faraday Cage of acable joint may be supported when it is enclosed by non-rigid material;

FIG. 22 shows another embodiment of support for a Faraday Cage;

FIG. 22A shows a cross section through part of a joint employing thesupport member of FIG. 22;

FIGS. 23 and 23A show embodiments in section of a seal along thelongitudinal edges of the two half shells of the housing of the joint;

FIG. 23 B shows a cross-section through a modified joint showing alongitudinal closure mechanism;

FIG. 24 is an isometric view of one embodiment of a completed joint; and

FIG. 25 is a side view of a further embodiment of housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the in-line joint is formed between twosubstantially identical polymeric cables 2, 4. The respective outerjackets 6, 8, screen wires 10, 12 screen layers (semi conducting orconducting) 14, 16, primary dielectric layers 18, 20, and conductors 22,24, are successively cut back in standard manner, with the screen wires10, 12 being folded back over their respective jackets 6, 8 forsubsequent interconnection (not shown) across the joint so as tomaintain earth continuity. The conductors 22, 24 are electricallyinterconnected by means of a crimp connector 26, although any othersuitable type of connector may be used. Electrical stress control of theconductor connection thus made is provided by a member comprising twogenerally semi-cylindrical half shells 28, 30 made of conductivepolymeric material that are brought together around the crimp connector26 between the two cables and which longitudinally extends a short wayover the cable dielectric layers 18, 20. Each half shell 28, 30 hasthree inwardly-directed projections 32 that make electrical contact withthe crimp 26 to ensure that the half shells 28, 30, and the conductivecomponents enclosed therewithin are maintained at the same electricalpotential, namely the potential of the cable conductors. The half shells28, 30 thus provide a Faraday Cage effect around the crimp 26 andexposed conductors 22, 24. It should be noted that the half shells 28,30 do not seal on to the cable dielectrics 18, 20.

Stress-relief cones 34, 36 are provided for the respective cables 2, 4and are located so as to provide a conical surface directed away fromthe cut back ends of respective shields 14, 16 in the usual manner. Thestress cones 34, 36 are formed of a conductive rubber and are .eachprovided as a pair of half cones for assembling around the cables 2,4after the electrical connection therebetween has been made.

The stress cones 34, 36 and Faraday Cage 28, 30, are completely enclosedwithin a pair of generally semi-cylindrical outer hinged half shells 38,40 made of conductive polymeric material, namely carbon-filledpolypropylene, that fit together to form a cylindrical housing thatclamps around the cables 2, 4 so as to seal down on to respective cablejackets 6, 8 to each side of the joint.

An electrically insulating support cradle, formed as twosemi-cylindrical components 42, 44, is secured to the outer surface ofthe Faraday Cage 28, 30 and to the inner surface of the outer housing38, 40, so as positively to locate the Faraday Cage 28, 30 bothlongitudinally and radially within the joint and thereby to ensureelectrical isolation of the Faraday Cage from the outer housing.

The space remaining within the housing 38, 40 around and within cradle42, 44 and the Faraday Cage 28, 30, and longitudinally bounded by thestress cones 34, 36, is completely filled with anelectrically-insulating silicone gel 46.

The components of the joint are assembled by locating respective ones ofthe support cradle 42, 44, the Faraday Cage 28, 30 and the stress cones34, 36 within respective housing half-shells 38, 40, pouring the gel 46in liquid, un-cured form into each half shell up to its rim, and thenallowing the gel to cure. The cables 2, 4 are then prepared by being cutback, the conductors 22, 24 secured together by the crimp connector 26,and insulating, stress relief and screening are then provided simply byclamping the prepared housing half shells 38, 40 therearound. Thesecuring together of the half-shells 38, 40 brings together thegenerally planar surfaces of each portion of the gel 46, which thenprovides a high dielectric strength interface, not only gel-to-gel wherethe half shells meet, but also on to the enclosed components of thecables 2, 4, such as the dielectrics 18,20.

As the two half shells 38, 40 are closed around the jointed cables 2, 4,the gel 46 is subjected to a compressive force such that it flows aroundall of the components and conforms therewith. Air present around thejointed cables is thus forced away and its place taken by the deformedgel 46. It will be appreciated that before closure the gel 46substantially fills the half-shells 38,40 to their rims. Accordingly,upon closure around the jointed cables, a quantity of the gel 46 isdisplaced, and this has to be accommodated by the construction of thejoint. Furthermore, thermally cycling of the power cables 2, 4 givesrise to expansion of the gel, which also has to be accommodated.Embodiments of the joint disclosed hereinafter solve these problems.

Further details and features of the general construction and assembly ofsuch a joint are given in pending U.S. patent application Ser. No.08/138360 (WO 95/11543) of Raychem Corporation, the entire contents ofwhich are included herein by virtue of this reference.

The following FIGS. 2 to 25 show in further detail specific features ofthe cable joint of FIG. 1, and variations thereof, each in accordancewith various aspects of the present invention. It is to be understoodthat all combination of two or more features herein described areconsidered as embodiments of the present invention, except where such acombination is obviously non-operable.

Referring to FIGS. 2 and 2A, a stress cone 34A, in two generallysemi-cylindrical parts, is a modification of the basically configuredstress cone 34 of FIG. 1. It is formed within the housing 40 so as todefine an annular void 50 therewith. The cone 34A extends away from theedge of the screen 14 with a leading edge 52 of the cone 34A sealing onto the housing 40.

The gel 46 is seen to fill the volume within the housing 40 around thecable dielectric 18. FIG. 2 shows the arrangement of the cable joint oninstallation, with the cable unpowered and cold. In operation, the cableconductor can reach operating temperatures of up to 95 degrees Celcius,and in some instances even higher. Under these condition the gel in thejoint, typically being a quantity between about 200 grams and about 300grams, can extend up to 20% in volume. and with a rigid outer housing40, the expansion has to be accommodated within the configuration of thejoint. In the present embodiment, expansion of the gel 46, acting on therelatively soft rubber of the stress cone 34A is arranged to compressthe void 50, as seen in FIG. 2A. As the gel 46 contracts on cooling, theresilience of the cone 34A, and in particular of its leading edge 52acts on the gel so as to maintain its sealing pressure around thevarious components of the joint. Thus, the formation of voids around thejoint components in the electrically highly-stressed areas between thetwo symmetrically disposed stress cones 34A and 36A (the latter notbeing shown) at each end of the joint is prevented, since sufficientpressure is maintained on the gel 46 under all conditions. It is to benoted that the deformation of the leading edge 52 of the stress cone 34Ais arranged, by suitable positioning of the void 50, to take place at aradial distance outwardly of the cable 2 such that control of theelectric field at the cut-back end of the screen 14 is not diminished,at least not to any significant extent.

FIG. 3 shows a further modified stress cone 34B located within thehousing 40, in which an aperture 60 at a radially-outward extremity ofthe cone is closed to entry of the gel 46 by a plunger 62 that isbiassed outwardly by a spring 64. Thus, as gel 46 expands, the pressureexerted on the plunger 62 forces it into the aperture 60 against theforce of the spring 64, and on relaxation of the gel 46, the restoringforce of the spring 64 maintains pressure on the gel 46 so as to preventthe formation of any undesirable voids in electrically-vulnerable areasof the joint.

FIGS. 4 and 4A show another embodiment of a stress-relief cone arrangedto accommodate expansion of the gel in a joint configured generally asshown in FIG. 1. The resilient cone 34C of these Figures is mountedwithin the outer housing 40 and has an aperture 70 adjacent to the innerwall thereof. The aperture 70 is open to receive gel 46 and to allowaccess of the gel to the interior of the cone bounded at its rear end,that is to say the end away from the crimp region of the joint, by awall portion 72 acting as a diaphragm of an expansion chamber 74. Inoperation, therefore, increase in volume of the gel 46 exerts a pressurethrough the aperture 70 on to the diaphragm 72, which stretchesaccordingly, and which tends to return to its natural un-stretched stateon relaxation of the gel.

The modified joint configuration of FIGS. 5 and 5A shows a stress cone34D provided with a cylindrical tubular extension 80 at its front endterminating in a lip 82 secured in the inner wall of the housing 40D.The housing 40D is domed partway around its circumference in the regionof the cone extension 80 so as to form a cavity 84 with the extension 80mounted as a flexible diaphragm thereacross. Increase in volume of thegel 46 within the joint thus urges the extension 80 locally to stretchinto the cavity 84. Continuous pressure is thus maintained on the gel 46as temperature variation leads to its increase or decrease in volume. Asshown in FIG. SA, the cavity 84 is vented by a channel 86 to a regionbehind the cone 34D so as to prevent build up of a vacuum. As can beseen from FIG. 5A, the expansion cavity 84 extends only partway aroundthe circumference of each of the half shells 38D, 40D of the housing inorder to allow for peripheral sealing of the half-shells of the joint bythe gel contained therein. The portion 80, which as shown is an integralextension of the stress cone 34D but which may be a separate component,is bonded directly so the housing 38D, 40D along each longitudinal edgethereof where the two half-shells mate, in order to prevent air beingtrapped between the portion 80 and the housing.

In a modification of the concept of FIG. 5 and SA, the housing 38, 40 isnot domed to define a cavity such as 84, but continues as a straightcylinder over and in contact with the diaphragm portion 80. In thisconfiguration, the extended portion 80, which may be a componentseparate from the stress cone 34, 36, is not bonded to the overlyinghousing except along the longitudinal edges as mentioned above. Thus,when the gel 46 contracts, the portion 80, under the action of airpressure through the vent 86, follows the movement of the gel towardsthe centre of the joint, moving away from the inner wall of the housingas it does so. It is envisaged that the component 80 may comprise aliner extending completely longitudinally of the joint, and in thisembodiment, it will be also bonded so the housing 38, 40 in the regionsurrounding the Faraday Cage 28, 30 to maintain the electrical geometryof the joint in this region.

FIG. 6 shows part of one half of a joint 600 that combines concepts fromthe embodiments of FIGS. 3 and 4. The enclosing half-shell 602 of thejoint 600 has a longitudinally extending channel 604 in its outer wallextending along substantially its whole length at one circumferentiallocation. A spring 606 and plunger 608 are retained in each half (onlyone of which is shown) of the length of the channel 604. A substantiallyrigid half stress cone 610 is located within the half shell 602 and hasa channel 612 in its outer surface that extends from the front end ofthe cone 610 facing the gel filling 614 of the joint to the rear of thecone 610 and that is in communication with the housing channel 604. Gel614 can thus flow through the channel 612 between the cone 610 and thehousing 602, enter the housing channel 604 and thus act on or be actedupon by the spring-biassed plunger 608, in order to accommodatedisplacement or expansion of the gel.

The still further modified stress cone 34E of FIGS. 7, 7A and 7B isprovided with a modified diaphragm feature described above with respectto FIGS. 5 and 5A, together with certain range-taking features. Thus,the cone 34E has an aperture 90 (FIGS. 7A and 7B) at its front,gel-facing conical surface, as can be seen particularly in FIG. 7Ashowing a section through the cone. Gel 46 (not shown) enters throughthe aperture 90 and may exert a force on the outer surface of the stresscone, acting as a diaphragm 92 to extend into a displacement cavityformed in the housing (not shown) in a manner analogous to thatdescribed with reference to FIGS. 5 and 5A, but with the cavity formedin that part of the housing enclosing the body of the cone 34E.Alternatively, or additionally, the rear surface 94 of the aperture 90can act as a diaphragm in a manner analogous to that described withreference to FIGS. 4 and 4A.

The stress cone 34E has in addition. range -taking features that allowit to be used with cables of various diameters, within a given range.Thus, the stress cone 34E has three apertures 96, 98, 100 therein,vented to its rear surface (FIGS. 7 and 7A), defining two channels 102,104 therebetween that extend transversely into the cone andlongitudinally partly thereinto from the rear surface. The operation ofthe range-taking ability of the case 34E, and its co-operation with theouter housing, are described hereafter with reference to FIGS. 9 and 10.

The embodiments discussed above allow for extension of the volume of thegel 46 in the joint as it increases its temperature, either due toincrease in the temperature of the enclosed cable in operation, and/ordue to increasing ambient temperature around the outer housing 40.However, since in the usual condition of the joint, that is to say, forthe greater part of its lifetime, the gel 46 will be hot and thusexpanded, it is also envisaged that accommodation may instead be madefor contraction under certain conditions, such as for example when thepower through the cables is interrupted. The gel-displacementarrangement, in so far as it relies upon movement of a resilient member,may then be arranged so as to be in its relaxed condition whilst the gelis extended, and be arranged to stretch upon cooling and reduction involume of the gel, thereby to maintain pressure on the gel. FIG. 8 showsan embodiment of such an arrangement, in which the stress-relief cone34F has an aperture 110 locally at its outer circumference adjacent thehousing wall 60F. The housing 60F has a cut-out portion 112 adjacent theaperture 110 but is separated therefrom by a flexible membrane 114secured thereacross. The cutout 112 is vented to the rear of the stresscone 34F. The membrane 114 and its securement to the housing 60F isarranged such that under normal operating conditions of the joint, theexpanded gel 46 fills the aperture 110 and the diaphragm 114 is in itsrelaxed state. Upon cooling, and thus contraction of the gel 46, thediaphragm 114 is urged by excess air pressure from the venting chamber(not shown) to stretch, to extend into the aperture 110, and to adoptthe position shown in dotted outline, and thus to maintain pressure onthe gel 46.

It will be appreciated that the concept described with reference to FIG.8 could be applied to other arrangements. for example that describedwith reference to FIGS. 5 and 5A.

FIGS. 9 and 10 show embodiments of a range-taking arrangement forproviding a seal on to one of number elongate substrates of variousdiameters, exemplified by being applied to a stress-relief cone for use,for example, in the joint of FIG. 1. A housing 160 is of a relativelyrigid, conductive polymeric, polypropylene, material, and is in the formof two generally-cylindrical half-shells (only one of which is shown).At each end, the housing 160 is provided with two substantially paralleland inwardly-directed planar projections or fins 162 for engaging withrespective stress relief cones 164, each of which is also formed as twohalf cones. The stress cones 164 are formed from a relatively flexibleconductive rubber material and have slots 166 therein for receivingrespective ones of the projections 162. As can be seen from FIG. 10,when two such arrangements as described with reference to FIG. 9 arebrought together around a cable 168, the softer material of the, nowfully-formed stress cone 164 will tend to stretch over the outerdiameter of the cable 168 and will tend to separate along the joinsurface 170 of the two halves of the joint enclosure. However, therigidity of the projecting fins 162 extending into the stress cone 164on each side of the cable 168 restrain movement of the cone 164 awayfrom the cable 168 at the interface 170.

In the example shown in FIGS. 9 and 10, the stress cone 164 is providedwith apertures 172 in its flexible material, opening towards the rear ofthe conical surface, that is to say at its surface away from the crimpregion of the joint, on each side of the slots 166, which arere-inforced in the assembled configuration by the fins 162. Theapertures 172 enhance the ability of the inner surface of the stresscone 164 to stretch over a cable 168 so as to accommodate cables oflarger size whilst maintaining a good seal therearound at the interface170. The central aperture 172 in particular defines an inner, semicylindrical membrane that can be stretched around the cable 168, withthe rigid reinforcing projections 162 urging the two halves of the cone164 into conformity with the enclosed cable 168 at the interface 170.

It will be appreciated that the reinforcing interengagement arrangementof FIGS. 9 and 10 allows conformity with elongate substrates other thanby means of using a stress-relief cone. The concept can be used forexample to provide a seal around a shaft, or as a bushing where a cable,which may be of one of a number of diameters, passes through a bulkhead.

Referring to FIGS. 11 and 12, a half cone 800, manufactured from aconductive rubber material, is a modification of the half cone 164 ofFIGS. 9 and 10. It will be appreciated that, like the half cone 164, thehalf cone 800 has a closed front end, and that one half cone will belocated at each end of each half shell that forms the closure around thecable joint (only part of one half-shell being shown in FIGS. 11 and12). At the rear (as shown) of the half cone 800, a large aperture 802extends to the closed front surface of the cone, and is radially closedby the half shell 804. The aperture 802 is divided into three portionsby a pair of fins 806 that extend generally radially from the innersurface of the half-shell 804, in a manner similar to the way in whichthe fins 162 extend from the housing half shell 160 as shown in theembodiment of FIG. 9. The fins 806 are disposed so as, in operation, tolie one on each side of the cable within the joint. A relatively thinwall portion 808 at the inner side of the half cone 800 is arched so as,in operation, to conform around an enclosed cable and so as to receiveand guide the free, inner ends of the fins 806. As shown in FIG. 11, thefins are positioned relatively close to the longitudinal axis of thejoint, and the length of the arched portion of the inner wall 808 of thehalf cone 800 is minimised. In this position of the fins 806, the halfcone 800 will conform to a minimum diameter size cable (not shown). Ascan be seen from FIG. 12, the fins 806 have a flexibility that allowsthem to splay outwards and to allow a greater length of the arched wallportion 808 to extend therebetween. In this position, the half cone 800will conform to a maximum diameter size cable. It is to be noted that inthis embodiment, unlike that of FIG. 9 and 10, the inner half conesurface 808 is not stretched. The presence of the fins 806, however,still ensures substantially complete conformity of the completed conearound a range of sizes of cable, without air pockets being present atthe interface of the two half cones adjacent the cable surface. It willbe appreciated that the flexibility of the fins 806 is such that theyare able to splay outwards around a larger diameter cable but that theyare relatively rigid with respect to the softer elastomeric material ofthe half cones 800.

An alternative, or additional, way of providing for expansion of the gel46 in the joint of FIG. 1, is shown with reference to FIG. 13A and alsowith reference to FIGS. 13B and 13C, each of which shows a Faraday Cagemodified from that illustrated at 28, 30 in FIG. 1. Referring to FIG.13A, the two half-shells 28A, 30A are formed from flexible conductivepolymeric material, and contain three apertures 120, therein. As the gel46 expands, the increased pressure is exerted on the half shells 28A,30A, which deform by compression of the apertures 120. Cooling of thegel leads to expansion of the volume of the apertures 120 and thus tothe maintenance of pressure on the gel 46.

A modification of the arrangement of FIG. 13A is shown in FIGS. 13B and13C, in which each end of the half-shells 28B and 30B is sealed on tothe cable dielectrics 18, 20 so as to define two apertures 122 locatedwithin the Faraday Cage 28B, 30B around the crimped conductors. As shownin FIG. 13C, the apertures 122 accommodate an increase of gel pressureby inward flexing of the half-shells 28B, 30B upon expansion of the gel46.

FIGS. 14 and 15 disclose two embodiments of the joint concept of FIG. 1in which change of volume of the sealant material 46 is accommodated bya modification of the configuration of the outer housing 40.

In the embodiment of FIG. 14, the generally rigid outer housing 40C isprovided as part of its surface with flexible wall 130 that is subjectto the pressure of the gel 46 (not shown) contained therein. To completethe rigidity of the housing 40C overall which may, in operation, beburied in the ground, a rigid cover 132 is arranged to fit over theflexible wall 130 to define a cavity therewith. A resilient block 134 ofrubber is located within the cavity. Thus, on expansion of the gel 46,the flexible wall 130 will transmit the pressure into compression of theblock 134 against the restraint of the rigid housing 40C, and oncontraction, the wall 130 will maintain pressure on the gel so as toprevent formation of voids around the joint.

The embodiment of FIG. 15 is arranged to achieve the same effect as thatof FIG. 14, but to this end each half of the housing 40D is made of arubber material and has a circumferential portion 140 of thinner sectionadjacent the stress cone 142 so as preferentially to expand, accommodateany increase in gel volume, and to exert a restoring force thereon.

Referring to FIGS. 16, 17 and 18 an elongate semi-cylindrical integralrubber moulding 1000 has a relatively thin wall intermediate section1002 (FIG. 17) and a pair of relatively thick wall end sections 1004that have a half-stress cone 1006 formed on the inside thereof (FIG.18). The moulding 1000 is arranged to be fitted into a rigid plasticouter case 1008 that is radially spaced therefrom along at least part ofthe intermediate section 1002. Displacement or expansion of the gelfilling material within the moulding 1000 results in flexing of theintermediate section 1002 into the expansion chamber provided by theouter case, preferably formed from a pair of half-shells, of thecompleted joint.

The rigid internal support members 150,160 discussed hereinafter withrespect to FIGS. 21, 22 and 22A, may be integrated into the rubbermoulding 1000 and located by snap-fitting into the outer plastic case.

Referring to FIGS. 19 and 20, two cables 1140 and 1142 are shownschemically jointed at 1144. A wraparound elastomeric insulating body1146 has fingers 1148 at each end thereof than can be tapered down toconform with the reduced diameter of the cables 1140, 1142 on each sideof the joint region 1144. One cylindrical closure member 1150 isinitially rolled on to each of the cables 1140, 1142. The closuremembers 1150 are formed from conductive rubber.

FIG. 20 shows the joint partially completed. The insulating body 1146,which may comprise a mating pair of half-shells rather than being of thewraparound configuration as shown, encloses insulating gel material 1152and may also contain solid insulation enclosing the gel sealant. Thebody 1146 is closed around the joint 1144 and the fingers 1148 broughtdown on the cables 1140, 1142. One conductive closure member 1150 isshown as having been uncurled from its parked position on the cable1140, so as to extend to just more than halfway across the body 1146.The other, still-parked closure member 1150 on cable 1142 will then beuncurled so as to overlap the first closure member. In this way, theinsulating body 1146 including both its fingered end-sections 1148, andthe entire cable joint region is enclosed within the two conductiveouter members 1150.

FIGS. 21, 22 and 22A disclose embodiments of cable joint in which aconductive component such as a Faraday Cage, can be supported within thejoint when it is otherwise enclosed by non-rigid material, and inparticular can be positively located with respect to an outer conductivehousing.

In FIG. 21, the arcuate Faraday Cage 28c is made of conductive polymericmaterial, is disposed in silicone gel sealant 46 as hereinbeforedescribed, is radially spaced (by means not shown) from the enclosedcrimped conductors (not shown), and is located axially between stresscones 34G and 36G. These components are enclosed within the outerhousing 40 of conductively - filled polypropylene. Under certainconditions, and especially when the temperature of the gel 46 isincreased, there is a likelihood that the conductive cage 28c could movelaterally within the gel 46 towards the housing 40, which is at earthpotential, and thus form a short circuit from the high voltage of thecable conductors. In this embodiment, movement of the cage 28C isprevented by employing an insulating polymeric support cradle or spacer150. The cradle 150 is arcuate and mounted in the annular gap betweenthe cage 28C and the housing 40, and, like those components, is formedas two half-shells. Each half of the spacer 150 is provided with aseries of projections on each of its curved surfaces so as to distanceit from both the cage 28C and the housing 40, thereby to allow gel 46substantially completely to fill the space therearound. The spacer 150is arranged to provide good physical interengagement with both the cage28C and the housing 40, for example by means of interlocking projectionsand apertures and/or a snap-fitting mechanism, thereby securely tomaintain the conductive cage 28c in position both radially andlongitudinally within the joint.

FIGS. 22 and 22A show another variation of support member for use with aFaraday Cage. Referring to these FIGS., the polymeric insulating supportmember 160 is of partial semi-cylindrical configuration, being flangedat each end so as to provide for an annular channel 162 between thesupport 160 and the outer housing 60 when used in operation to supportthe Faraday Cage 28. As shown in FIG. 22A, which is a section throughone of the half-shell components of the joint, the Faraday Cage 28 andhousing 60 are fully semi-cylindrical so that when brought together withthe corresponding half-shell around the crimped conductors (not shown),the cylindrical surfaces thereof are completed. The two half shells ofthe support member (only the one 160, being shown) however extend forless than 180degrees, with the region therebetween, as well as thechannel 162, being filled by the gel 46, to provide a gel/gel radialinterface between the Faraday Cage 28 and the housing 60 on closure ofthe two half shells around the crimp region. The support member 160 maybe mechanically interlocked, as described with reference to theembodiment of FIG. 21 for example, with both the Faraday Cage 28 and thehousing 40 of its respective half shell so as securely to locate theFaraday Cage 28 within the joint.

The support spacers 150, 160 may but need not extend longitudinallyco-terminously with the associated Faraday Cage.

In a further modification, it is envisaged that the support member maybe moulded integrally with the Faraday Cage and/or the housing. In sucha construction, the moulding operation itself may exclude air from themoulded surface of the support member, thus avoiding the need to allowthe gel 46 to have access to any interface between the support memberand the Faraday Cage and/or housing.

FIGS. 23 and 23A show two different configurations by which thelongitudinal edges of the two half shells of the housing of a cablejoint can be interlocked. In each case, one edge 180,180A is providedwith a groove 182,182A extending therealong, being of trapezoidalsection in FIG. 23 and of key-hole section in FIG. 23A. The grooves182,182A are filled with gel, advantageously the same as that providingthe bulk insulation of the joint. The opposing edges 184,184A of thehousing are provided with correspondingly-shaped projections 186,186A.Upon closure of the two half shells of the housing around the electricalconnection, the projection 186,186A engages the associated groove182,182A, and the gel forms a seal therebetween.

Referring to FIG. 23B, a cross-section is shown of a jointed cableschematically at 200 partially embedded in gel 202 that is contained ineach part of a pair of half-shells 204, 206. The half-shells 204, 206are substantially semi-cylindrical and are hinged together at 208 alongone pair of longitudinal edges. The hinged cylindrical housing formed bythe two half-shells is closed around the jointed cables and FIG. 23Brepresents the situation just prior to closure of the housing. Thelongitudinal edges of the half-shells 204, 206 opposite the hinge 208are provided with a co-operating tongue 210 and groove 212 arrangementalong the major part of the length of the housing which contains the gel202 that is to be urged into conformity around the enclosed jointedcables. The tongue 210 is of such a length, in the circumferentialdirection, that on closure of the two half-shell 204, 206, it engagesthe groove 212 before pressure on the gel 202 is sufficient to exude itsideways out of the housing. In this way, all the gel 202 is completelycontained within the closed housing circumferentially, thus avoiding anypossible shearing of the gel that could subsequently lead to thecreation of voids within the housing.

Positive locking together of the two half-shells 204, 206, is achievedby a plurality of discrete projections 214 along the outer surface ofthe tongue 210 which snap into co-operating apertures 216 in the outerwall of the groove 212.

Sealing of the housing against ingress of moisture, air, dust or othercontaminants around its periphery at the interface of the twohalf-shells 204, 206 is enhanced by the provision of a ridge 218 aroundthe entire periphery of the half-shell 206 that tightly engages with amating peripheral depression 220 in the half-shell 204.

Finally, the two half-shells may be secured together by toggle clips orother suitable fastening means applied externally of the closed housing.

Referring to FIG. 24, a joint between two screened cables 1160, 1162 isenclosed within a two-part housing 1164. A slot 1166 is cut axially intothe housing 1164 at each end thereof in longitudinal alignment, and thescreen wires 1168, 1170 of the cables 1160, 1162 respectively arebrought out through the slots 1166 and crimped together at 1172 over theouter housing surface. The connecting together of the screen wires 1168,1170 and their engagement within the slots 1166 in this manner, preventsthe housing 1164 from moving either rotationally or longitudinally withrespect to the jointed cables.

Referring to FIG. 25, the housing 1180 is formed from twosemi-cylindrical half-shells that are hinged together at 1182 along itscentral portion, and that are sealed by a tongue and groove arrangementaround their mating peripheries. Beyond a tapered portion towards eachend of the housing 1180, a cylindrical portion 1186 is formed between apair of ribs 1188 that extend around the circumference of the housing.The housing 1180 is secured on to the enclosed jointed cables by meansof tape, a tie-wrap, a roll-spring or the like 1190 that is wrappedaround the cylindrical housing portions 1186. To enhance the sealing,and to assist the retention, of the housing on the cables, mastic orother sealant material may be located between the housing portions 1186and the underlying cable jackets. The sealant material may be applied tothe cables as a wrapping, or may be retained by the housing 1180.

We claim:
 1. An enclosure arranged to enclose a connection between twoelectrically conductive components, the enclosure comprising a housingand an electrically conductive polymeric member disposed therein, theconductive polymeric member being arranged, in operation, to makeelectrical contact with an sealingly enclose the connection, wherein aspace between the conductive polymeric member and the housing is, inoperation, substantially filled with a compressible sealant material,and wherein the conductive polymeric member is resilient, substantiallyto prevent, in operation, the formation of voids within the housingoutside the conductive polymeric member and further wherein theconductive polymeric member has at least on e void or gaseous entrapmentcompletely contained within the conductive polymeric member, the atleast one void or gaseous entrapment being subject to t he pressure ofthe sealant material via the resilient conductive polymeric member. 2.An enclosure according to claim 1, wherein the sealant material is anoil-extended polymeric material.
 3. An enclosure according to claim 1,wherein the conductive polymeric member is arranged, in operation, toexert pressure on the sealant material.
 4. An enclosure according toclaim 1, wherein the sealant material comprises a gel.
 5. An enclosureaccording to claim 1, wherein the housing comprises a conductive outersurface.
 6. An enclsoure according to claim 1, wherein the housingcomprises a resilient portion to accommodate a change in volume, ordisplacement, of the sealant material.
 7. An enclosure according toclaim 1, further comprising location means arranged to support theconductive polymeric member and to maintain the position of theconductive polymeric member within the sealant material.
 8. An enclosureaccording to claim 1, wherein the housing comprises at least twointerengaging parts, each of which contains one part of the electricallyconductive polymeric member and a portion of the sealant material.
 9. Anenclosure according to claim 1, wherein at least one of the conductivecomponents comprises an electric power cable.
 10. An enclosure arrangedto enclose a connection between two electrically conductive components,the enclosure comprising a housing, an electrically conductive polymericmember disposed therein, and a stress relief cone; the conductivepolymeric member being arranged, in operation, to make electricalcontact with and sealingly enclose the connection; the stress reliefcone, in operation, being arranged to be disposed around one of theconductive components within the housing; wherein a space between theconductive polymeric member and the housing is, in operation,substantially filled with a compressible sealant material, and whereinthe conductive polymeric member is resilient, substantially to prevent,in operation, the formation of voids within the housing outside theconductive polymeric member and further wherein the stress relief conecomprises resilient aperture means whose volume is arranged to change inresponse to change of volume of the sealant material.
 11. An enclosureaccording to claim 10, wherein the sealant material is an oilextendedpolymeric material.
 12. An enclosure according to claim 10, wherein theconductive polymeric member is arranged, in operation, to exert pressureon the sealant material.
 13. An enclosure according to claim 10, whereinthe sealant material comprises a gel.
 14. An enclosure according toclaim 10, wherein the housing comprises a conductive outer surface. 15.An enclsoure according to claim 10, wherein the housing comprises aresilient portion to accommodate a change in volume, or displacement, ofthe sealant material.
 16. An enclosure according to claim 10, furthercomprising location means arranged to support the conductive polymericmember and to maintain the position of the conductive polymeric memberwithin the sealant material.
 17. An enclosure according to claim 10,wherein the housing comprises at least two interengaging parts, each ofwhich contains one part of the electrically conductive polymeric memberand a portion of the sealant material.
 18. An enclosure according toclaim 10, wherein at least one void or gaseous entrapment is, inoperation, arranged to be sealingly contained between the conductivepolymeric member and the connection between the two conductivecomponents, and is subject to the pressure of the sealant material viathe conductive polymeric member.
 19. An enclosure according to claim 10,wherein the conductive polymeric member has at least one void or gaseousentrapment completely contained within the conductive polymeric member,the at least one void or gaseous entrapment being subject to thepressure of the sealant material via the resilient conductive member.20. An enclosure according to claim 10, wherein at least one of theconductive components comprises an electric power cable.
 21. Anenclosure according to claim 10, wherein the stress relief conecomprises (a) a relatively rigid component and (b) a relativelyresilient component, wherein the rigid component, in operation, isarranged to urge the resilient component into substantially completeconformity around the cable.
 22. An enclosure according to claim 21,wherein the sealant material is an oil-extended polymeric material. 23.An enclosure according to claim 21, wherein the conductive polymericmember is arranged, in operation, to exert pressure on the sealantmaterial.
 24. An enclosure according to claim 21, wherein the sealantmaterial comprises a gel.
 25. An enclosure according to claim 21,wherein the housing comprises a conductive outer surface.
 26. Anenclsoure according to claim 21, wherein the housing comprises aresilient portion to accommodate a change in volume, or displacement, ofthe sealant material.
 27. An enclosure according to claim 21, furthercomprising location means arranged to support the conductive polymericmember and to maintain the position of the conductive polymeric memberwithin the sealant material.
 28. An enclosure according to claim 21,wherein the housing comprises at least two interengaging parts, each ofwhich contains one part of the electrically conductive polymeric memberand a portion of the sealant material.
 29. An enclosure according toclaim 21, wherein at least one void or gaseous entrapment is, inoperation, arranged to be sealingly contained between the conductivepolymeric member and the connection between the two conductivecomponents, and is subject to the pressure of the sealant material viathe conductive polymeric member.
 30. An enclosure according to claim 21,wherein the conductive polymeric member has at least one void or gaseousentrapment completely contained within the conductive polymeric member,the at least one void or gaseous entrapment being subject to thepressure of the sealant material via the resilient conductive polymericmember.
 31. An enclosure according to claim 21, wherein at least one ofthe conductive components comprises an electric power cable.